The present invention is directed to improved photosensitive imaging members. More specifically, the present invention is directed to photosensitive imaging members containing improved polymeric binders. One embodiment of the present invention is directed to an imaging member which comprises a conductive substrate, a photogenerating material, a charge transport material, and a polymeric binder comprising (a) a first polymer comprising a polycarbonate, and (b) a second polymer of the formula ##STR1## wherein x is an integer of 0 or 1, A is ##STR2## or mixtures thereof, B is ##STR3## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR4## wherein z is an integer of from 2 to about 20, ##STR5## wherein u is an integer of from 1 to about 20, ##STR6## wherein w is an integer of from 1 to about 20, ##STR7## or mixtures thereof, C is ##STR8## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the numbers of repeating units.
The formation and development of images on the surface of photoconductive materials by electrostatic means is well known. The basic electrophotographic imaging process, as taught by C. F. Carlson in U.S. Pat. No. 2,297,691, entails placing a uniform electrostatic charge on a photoconductive imaging member, exposing the imaging member to a light and shadow image to dissipate the charge on the areas of the imaging member exposed to the light, and developing the resulting electrostatic latent image by depositing on the image a finely divided electroscopic material known as toner. The toner will normally be attracted to those areas of the imaging member which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This developed image may then be transferred to a substrate such as paper. The transferred image may subsequently be permanently affixed to the substrate by heat, pressure, a combination of heat and pressure, or other suitable fixing means such as solvent or overcoating treatment.
Imaging members for electrophotographic imaging systems comprising selenium alloys vacuum deposited on substrates are known. Imaging members have also been prepared by coating substrates with photoconductive particles dispersed in an organic film forming binder. Coating of rigid drum substrates has been effected by various techniques such as spraying, dip coating, vacuum evaporation, and the like. Flexible imaging members can also be manufactured by processes that entail coating a flexible substrate with the desired photoconducting material.
Some photoresponsive imaging members consist of a homogeneous layer of a single material such as vitreous selenium, and others comprise composite layered devices containing a dispersion of a photoconductive composition. An example of a composite xerographic photoconductive member is described in U.S. Pat. No. 3,121,006, which discloses finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. Imaging members prepared according to the teachings of this patent contain a binder layer with particles of zinc oxide uniformly dispersed therein coated on a paper backing. The binders disclosed in this patent include materials such as polycarbonate resins, polyester resins, polyamide resins, and the like.
Photoreceptor materials comprising inorganic or organic materials wherein the charge generating and charge transport functions are performed by discrete contiguous layers are also known. Additionally, layered photoreceptor members are disclosed in the prior art, including photoreceptors having an overcoat layer of an electrically insulating polymeric material. Other layered photoresponsive devices have been disclosed, including those comprising separate photogenerating layers and charge transport layers as described in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Photoresponsive materials containing a hole injecting layer overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin, are disclosed in U.S. Pat. No. 4,251,612, the disclosure of which is totally incorporated herein by reference. Examples of photogenerating layers disclosed in these patents include trigonal selenium and phthalocyanines, while examples of transport layers include certain aryl diamines as illustrated therein.
In addition, U.S. Pat. No. 3,041,167 discloses an overcoated imaging member containing a conductive substrate, a photoconductive layer, and an overcoating layer of an electrically insulating polymeric material. This member can be employed in electrophotographic imaging processes by initially charging the member with an electrostatic charge of a first polarity, followed by exposing it to form an electrostatic latent image that can subsequently be developed to form a visible image.
Japanese Patent Publication 63-247757 A2, the disclosure of which is totally incorporated herein by reference, discloses an electrophotographic photosensitive body consisting of a body in which a photoconductive layer laminated on a conductive support contains a charge generating substance and/or a charge transporting substance, and at least one polyether ketone polymer consisting of structural units which can be expressed by the following general formulae (I) and (II) ##STR9## wherein m is 0 or 1 and Ar indicates ##STR10## wherein R is an alkyl group, n is 0, 1, or 2, and X indicates ##STR11## with R' and R" each independently indicating --H, --CH.sub.3, --C.sub.2 H.sub.5, ##STR12## wherein the proportion of structural units in the polymer expressed by the general formula (I) is from 0.1 to 1.0 and the proportion of structural units in the polymer expressed by the general formula (II) is 0 to 0.9.
U.S. Pat. No. 5,336,577 (Spiewak et al.), the disclosure of which is totally incorporated herein by reference, discloses a thick organic ambipolar layer on a photoresponsive device which is simultaneously capable of charge generation and charge transport. In particular, the organic photoresponsive layer contains an electron transport material such as a fluorenylidene malonitrile derivative and a hole transport material such as a dihydroxy tetraphenyl benzadine containing polymer. These may be complexed to provide photoresponsivity, and/or a photoresponsive pigment or dye may also be included.
U.S. Pat. No. 4,801,517 (Frechet et al.), the disclosure of which is totally incorporated herein by reference, discloses an electrostatographic imaging member and an electrophotographic imaging process for using the imaging member in which the imaging member comprises a substrate and at least one electroconductive layer, the imaging member comprising a polymeric arylamine compound represented by the formula ##STR13## wherein n is between about 5 and 5,000, m is 0 or 1, Z is selected from certain specified aromatic and fused ring groups, Ar is selected from certain specified aromatic groups, R is selected from certain specified alkyl groups, Ar' is selected from certain specified aromatic groups, and R' and R" are independently selected from certain specified alkylene groups.
U.S. Pat. No. 4,806,443 (Yanus et al.), the disclosure of which is totally incorporated herein by reference, discloses an electrostatographic imaging member and an electrophotographic imaging process for using the imaging member in which the imaging member comprises a substrate and an electroconductive layer, the imaging member comprising a polymeric acrylamine compound represented by the formula ##STR14## wherein n is between 5 and about 5,000, m is 0 or 1, y is 1, 2, or 3, Z is selected from certain specified aromatic and fused ring groups, Ar is selected from certain specified aromatic groups, Ar' is selected from certain specified aromatic groups, and X' is an alkylene radical selected from the group consisting of alkylene and isoalkylene groups containing 2 to 10 carbon atoms. The imaging member may comprise a substrate, charge generation layer, and a charge transport layer.
U.S. Pat. No. 4,806,444 (Yanus et al.) and U.S. Pat. No. 4,935,487 (Yanus et al.), the disclosures of each of which are totally incorporated herein by reference, disclose an electrostatographic imaging member and an electrophotographic imaging process for using the imaging member in which the imaging member comprises a substrate and an electroconductive layer, the imaging member comprising a polymeric arylamine compound represented by the formula ##STR15## wherein n is between about 5 and about 5,000, m is 0 or 1, Z is selected from certain specified aromatic and fused ring groups, Ar is selected from certain specified aromatic groups, and Ar' is selected from certain specified aromatic groups. The imaging member may comprise a substrate, charge generation layer, and a charge transport layer.
U.S. Pat. No. 4,818,650 (Limburg et al.) and U.S. Pat. No. 4,956,440 (Limburg et al.), the disclosures of each of which are totally incorporated herein by reference, disclose an electrostatographic imaging member and an electrophotographic imaging process for using the imaging member in which the imaging member comprises a substrate and at least one electroconductive layer, the imaging member comprising a polymeric arylamine compound represented by the formula ##STR16## wherein R is selected from the group consisting of --H, --CH.sub.3, and --C.sub.2 H.sub.5, m is between about 4 and about 1,000, A is selected from the group consisting of an arylamine group represented by the formula ##STR17## wherein m is 0 or 1, Z is selected from certain specified aromatic and fused ring groups that also contain an oxygen or sulfur atom, certain linear or cyclic hydrocarbon groups, and certain amine groups, Ar is selected from certain specified aromatic groups, Ar' is selected from certain specified aromatic groups, and B is selected from the group consisting of the arylamine group as defined for A and EQU --Ar--V).sub.n Ar--
wherein Ar is as defined above and V is selected from an oxygen or sulfur atom, certain linear or cyclic hydrocarbon groups, or a phenylene group, and at least A or B contains the arylamine group. The imaging member may comprise a substrate, charge generation layer, and a charge transport layer.
U.S. Pat. No. 5,030,532 (Limburg et al.), the disclosure of which is totally incorporated herein by reference, discloses an electrostatographic imaging member comprising a support layer and at least one electrophotoconductive layer, said imaging member comprising a polyarylamine polymer represented by the formula ##STR18## wherein n is between about 5 and about 5,000, or 0 if p&gt;0, o is between about 9 and about 5,000, or is 0 if p&gt;0 or n=0, p is between about 2 and about 100, or is 0 if n&gt;0, X' and X" are independently selected from a group having bifunctional linkages, Q is a divalent group derived from certain hydroxy terminated arylamine reactants, Q' is a divalent group derived from a hydroxy terminated polyarylamine containing the group defined for Q and having a weight average molecular weight between about 1,000 and about 80,000, and the weight average molecular weight of the polyarylamine polymer is between about 10,000 and about 1,000,000.
Copending application U.S. Ser. No. 08/976,004, filed concurrently herewith, with the named inventors Timothy J. Fuller, Leon A. Teuscher, John F. Yanus, Damodar M. Pai, Kathleen M. Carmichael, Edward F. Grabowski, and Paul F. Zukoski, now U.S. Pat. No. 5,814,426, the disclosure of which is totally incorporated herein by reference, discloses an imaging member which comprises a conductive substrate, a photogenerating material, and a binder comprising a polymer selected from (a) those of the formulae ##STR19## wherein x is an integer of 0 or 1, A is ##STR20## or mixtures thereof, B is ##STR21## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR22## wherein z is an integer of from 2 to about 20, ##STR23## wherein u is an integer of from 1 to about 20, ##STR24## wherein w is an integer of from 1 to about 20, ##STR25## or mixtures thereof, C is ##STR26## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the number of repeating units; (b) those of the formulae ##STR27## wherein x is an integer of 0 or 1, A is ##STR28## or mixtures thereof, B is ##STR29## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR30## wherein z is an integer of from 2 to about 20, ##STR31## wherein u is an integer of from 1 to about 20, ##STR32## wherein w is an integer of from 1 to about 20, ##STR33## or mixtures thereof, C is ##STR34## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the number of repeating units; (c) those of formulae I, III, IV, VII, or VIII wherein x is an integer of 0 or 1, A is ##STR35## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR36## wherein z is an integer of from 2 to about 20, ##STR37## wherein u is an integer of from 1 to about 20, ##STR38## wherein w is an integer of from 1 to about 20, ##STR39## or mixtures thereof, C is ##STR40## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the number of repeating units; (d) those of formulae I, III, IV, VII, and VIII wherein x is an integer of 0 or 1, A is ##STR41## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR42## wherein z is an integer of from 2 to about 20, ##STR43## wherein u is an integer of from 1 to about 20, ##STR44## wherein w is an integer of from 1 to about 20, ##STR45## or mixtures thereof, C is ##STR46## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the number of repeating units; or (e) those of formulae I, III, IV, VII, and VIII wherein x is an integer of 0 or 1, A is ##STR47## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR48## wherein z is an integer of from 2 to about 20, ##STR49## wherein u is an integer of from 1 to about 20, ##STR50## wherein w is an integer of from 1 to about 20, ##STR51## or mixtures thereof, C is ##STR52## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the number of repeating units.
Copending application U.S. Ser. No. 08/976,238, filed concurrently herewith, with the named inventors Timothy J. Fuller, Leon A. Teuscher, Damodar M. Pai, and John F. Yanus, the disclosure of which is totally incorporated herein by reference, discloses an imaging member which comprises a conductive substrate, a photogenerating material, and a polymer of the formula ##STR53## wherein x is an integer of 0 or 1, A is ##STR54## or mixtures thereof, B is ##STR55## wherein v is an integer of from 1 to about 20, EQU --(CH.sub.2 O).sub.t --
wherein t is an integer of from 1 to about 20, ##STR56## wherein z is an integer of from 2 to about 20, ##STR57## wherein u is an integer of from 1 to about 20, ##STR58## wherein w is an integer of from 1 to about 20, ##STR59## wherein (1) Z is ##STR60## wherein p is 0 or 1; (2) Ar is ##STR61## (3) G is an alkyl group selected from alkyl or isoalkyl groups containing from about 2 to about 10 carbon atoms; (4) Ar' is ##STR62## wherein s is 0, 1, or 2, ##STR63## and (6) q is 0 or 1; or mixtures thereof, wherein at least some of the "B" groups are of the formula ##STR64## or mixtures thereof, wherein R is an alkyl group, an aryl group, an arylalkyl group, or mixtures thereof, and m and n are integers representing the number of repeating units.
Generally the charge transport layer of a dual layer organic photoconductor employed in electrophotography consists of charge transport molecules dispersed in a single polymeric binder. Almost invariably, the binder of choice has been polycarbonate. Most transport molecules employed in the art disperse very well in polycarbonate and the devices containing transport layers of polycarbonate dispersed with molecules can be cycled for tens of thousands of cycles without any residual cycle-up caused by charge trapping in the transport layer. Phase separation of the molecules in the binder can lead to charge trapping and that can cause residual cycle-up. It would be advantageous to have a blend of two binders in which the charge transport molecules are dispersed. If the blend of polymers can be accomplished without phase separation, then it would be possible to tailor many properties of the dual layer device. The properties that can be improved include adhesion to the generator layer and the surface properties that affect the release properties, enabling easier transfer of the developed image and easy cleaning of the remaining toner particles. To be able to employ blends of polymers as binders for the transport layers, the two polymers should be compatible and should not phase separate. In addition, the charge transport molecules should disperse without phase separation in each one of the binders and in the blend of the two polymers.
While known compositions and processes are suitable for their intended purposes, a need remains for improved photosensitive imaging members. A need also remains for improved binders for photosensitive imaging members. In addition, there is a need for polymeric binders suitable for use in photogenerating layers in imaging members. Further, a need remains for polymeric binders suitable for use in charge transport layers in imaging members. Additionally, there is a need for polymeric binders with high glass transition temperatures. There is also a need for polymeric binders which enable the incorporation of high loadings of charge transport materials and/or plasticizers therein. In addition, a need remains for polymeric binders which exhibit good film properties and good adhesion to imaging member substrates. Further, a need remains for polymeric binders for imaging members which have high resistance to a wide variety of solvents. Additionally, a need remains for polymeric binders suitable for charge transport layers in imaging members which enable incorporation of charge transport materials such as N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine in the layer in amounts of 50 percent by weight and higher without resulting in severe plasticization. There is also a need for polymeric binders which can be coated onto photosensitive imaging members from a wide variety of solvents. Further, a need remains for polymeric binders in which charge transport molecules exhibit reduced or eliminated tendency to crystallize. In addition, there is a need for polymeric binders which have a reduced tendency to crystallize compared to widely used photoreceptor binder polymers. There is also a need for abrasion resistant and wear resistant photoconductive imaging members. Further, there is a need for photoconductive imaging members which are flat after oven drying. Additionally, there is a need for polymeric binders and transport polymers with improved wear and abrasion resistance compared to known polymers commonly used in photoconductive imaging members. A need also remains for photoconductive imaging members which are curl-free and stress-free after removal of coating solvents. In addition, a need remains for polymers suitable for use as adhesive layer materials in photoconductive imaging members. Further, a need remains for polymers suitable for use as protective overcoating layer materials in photoconductive imaging members. Additionally, a need remains for imaging members containing polymeric binders wherein the advantages of the commonly used polycarbonate binder materials, such as cost effectiveness, desirable mechanical characteristics, and the like, can be retained while also enabling additional advantages such as the ability to tailor the degree of adhesion between layers, the ability to tailor the surface properties of layers, increased solvent resistance, and the like, wherein these advantages are obtained by blending with the polycarbonate a second polymer which admixes well with the polycarbonate and exhibits little or no phase separation when admixed with the polycarbonate. There is also a need for imaging members containing polymeric binders comprising polymer blends which enable incorporation of charge transport molecules without causing charge trapping.